From a8d2cdb2cdbf8e2fea3cf9ba3dfccb59a9f9cff6 Mon Sep 17 00:00:00 2001
From: Enis Necipoglu <info@enisnecipoglu.com>
Date: Wed, 25 Mar 2026 13:07:13 +0300
Subject: [PATCH] Fix stdout/stderr deadlock in CmdHelper.RunCmdAndGetOutput
 (#25155)

* Fix stdout/stderr deadlock in CmdHelper.RunCmdAndGetOutput

Read stdout and stderr concurrently to prevent pipe buffer deadlock.
The sequential ReadToEnd() calls caused a hang when child processes
(e.g. dotnet build) produced enough stderr output to fill the OS
pipe buffer (~4KB on Windows), since the parent blocked on stdout
while the child blocked on stderr.

Made-with: Cursor

* Simplify Task.WhenAll result handling per review

Made-with: Cursor

* Add test for CmdHelper to prevent stdout/stderr deadlock

* Reduce timeout in deadlock test for CmdHelper to 10 seconds

---------

Co-authored-by: maliming <malimings@gmail.com>
---
 .../Volo/Abp/Cli/Utils/CmdHelper.cs           | 16 +++----
 .../Volo/Abp/Cli/Utils/CmdHelper_Tests.cs     | 47 +++++++++++++++++++
 2 files changed, 54 insertions(+), 9 deletions(-)
 create mode 100644 framework/test/Volo.Abp.Cli.Core.Tests/Volo/Abp/Cli/Utils/CmdHelper_Tests.cs

diff --git a/framework/src/Volo.Abp.Cli.Core/Volo/Abp/Cli/Utils/CmdHelper.cs b/framework/src/Volo.Abp.Cli.Core/Volo/Abp/Cli/Utils/CmdHelper.cs
index 5ccd9034cd..decf844131 100644
--- a/framework/src/Volo.Abp.Cli.Core/Volo/Abp/Cli/Utils/CmdHelper.cs
+++ b/framework/src/Volo.Abp.Cli.Core/Volo/Abp/Cli/Utils/CmdHelper.cs
@@ -1,7 +1,8 @@
-using System;
+using System;
 using System.Diagnostics;
 using System.IO;
 using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 using Microsoft.Extensions.Options;
 using Volo.Abp.DependencyInjection;
 
@@ -137,14 +138,11 @@ public class CmdHelper : ICmdHelper, ITransientDependency
 
             process.Start();
 
-            using (var standardOutput = process.StandardOutput)
-            {
-                using (var standardError = process.StandardError)
-                {
-                    output = standardOutput.ReadToEnd();
-                    output += standardError.ReadToEnd();
-                }
-            }
+            var outputTask = process.StandardOutput.ReadToEndAsync();
+            var errorTask = process.StandardError.ReadToEndAsync();
+
+            var results = Task.WhenAll(outputTask, errorTask).GetAwaiter().GetResult();
+            output = results[0] + results[1];
 
             process.WaitForExit();
 
diff --git a/framework/test/Volo.Abp.Cli.Core.Tests/Volo/Abp/Cli/Utils/CmdHelper_Tests.cs b/framework/test/Volo.Abp.Cli.Core.Tests/Volo/Abp/Cli/Utils/CmdHelper_Tests.cs
new file mode 100644
index 0000000000..1526a18d42
--- /dev/null
+++ b/framework/test/Volo.Abp.Cli.Core.Tests/Volo/Abp/Cli/Utils/CmdHelper_Tests.cs
@@ -0,0 +1,47 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using Shouldly;
+using Volo.Abp.Cli.Utils;
+using Xunit;
+
+namespace Volo.Abp.Cli.Utils;
+
+public class CmdHelper_Tests : AbpCliTestBase
+{
+    private readonly ICmdHelper _cmdHelper;
+
+    public CmdHelper_Tests()
+    {
+        _cmdHelper = GetRequiredService<ICmdHelper>();
+    }
+
+    [Fact]
+    public async Task RunCmdAndGetOutput_Should_Not_Deadlock_With_Large_Stdout_And_Stderr()
+    {
+        // Reproduces the deadlock bug where sequential ReadToEnd() on stdout then stderr
+        // would block indefinitely when both pipe buffers (~64 KB on Linux/macOS, ~4 KB on
+        // Windows) filled up simultaneously. The process was blocked writing to stderr while
+        // the caller was blocked waiting for stdout to close — a classic pipe deadlock.
+        //
+        // The fix reads both streams concurrently via ReadToEndAsync + Task.WhenAll, which
+        // drains both pipes at the same time and avoids the deadlock.
+        var command = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+            ? @"for /L %i in (1,1,3000) do @(echo stdout-line-%i & echo stderr-line-%i 1>&2)"
+            : "for i in $(seq 1 5000); do echo stdout-line-$i; echo stderr-line-$i >&2; done";
+
+        string output = null;
+        var cmdTask = Task.Run(() => output = _cmdHelper.RunCmdAndGetOutput(command));
+        var completed = await Task.WhenAny(cmdTask, Task.Delay(TimeSpan.FromSeconds(10)));
+
+        // The original sequential code deadlocked here; 10 s is a generous upper bound.
+        (completed == cmdTask).ShouldBeTrue(
+            "RunCmdAndGetOutput should not deadlock when both stdout and stderr produce large output");
+
+        await cmdTask;
+
+        output.ShouldNotBeNullOrWhiteSpace();
+        output.ShouldContain("stdout-line-");
+        output.ShouldContain("stderr-line-");
+    }
+}